I’m working on buying a used Graco 3400. It is half priced, but the guy doesn’t know how old it is, but says it works well, and won’t need to worry about warranty for a long time. He said he’d even take the pump apart and show me that it hasn’t been used much. My question is…he has had it in storage for quite a while, and it is sitting in a cold garage. He said he filled the unit with diesel fuel as it is better than paint thinner, because it has a lubricant in it. I know it does have lubricant, but wouldn’t it be hard to clean out, and wouldn’t it end up in the paint somehow. He says he has been painting for 30 years and never had a problem. He uses it for house painting and not striping.